Fuel burning apparatus



M. H. KUHNER Feb. 28, 1950 FUEL BURNING APPARATUS Filed March 21, 1945 3Shets-Sheet l /6 J8 A u M W; u llflnnnu u unuu awe/whom MAX H. AUHNEF?Feb. 28, 1950 KUHNER 2,498,761

FUEL BURNING APPARATUS Filed March 21, 1945 3 Sheets-Sheet 2 00000oooqoo oooooo Fig.5

MAX H. KUHNER Feb. 28, 1950 M. H. KUHNER FUEL BURNING APPARATUS 5Sheets-Sheet 3 Filed March 21, 1945 gwuc/wbo't MAX H. A UHNE'I? 006 0Fig. 4

Patented Feb. 28, 1950 FUEL BURNING APPARATUS Max H. Kuhner, Worcester,Mass., assignor to Riley Stoker Corporation, Worcester, Mass, acorporation of Massachusetts Application March 21, 1945, Serial No.583,959

4 Claims.

This invention relates to fuel burning apparatus, and more particularlyto apparatus arranged to produce steam by burning pulverized fuel insuspension.

It has been proposed heretofore to project pulverized fuel downwardlyinto the upper portion of a furnace chamber, and. to conduct the hotgases from the lower portion of the furnace chamber rearwardly intocontact with suitable heat absorbing surfaces, such as water tubes, forthe generation of steam. This method of burning fuel is known asdown-shot firing. Some of the air required for combustion enters thefurnace with the fuel, but the major part of the necessary air has beensupplied through openings in the front wall of the furnace. In theseprior steam generators many difliculties have been en countered inobtaining dependable ignition and complete combusion of the fuel.Considerable combustible material is deposited with the ash in thebottom of the furnace, and unburned carbon particles are carried out ofthe furnace by the hot gases. These troubles are particularly seriouswhen burning pulverized anthracite.

It is accordingly one object of the invention to overcome these variousdilliculties and to provide a fuel burning apparatus arranged for thedownshot firing of pulverized fuel and capable of maintaining steadyignition and efficient combustion.

It is a further object of the invention to provide a fuel burningapparatus particularly suitable for the down-shot firing of pulverizedanthracite and capable of burning such fuel in a dependable andefficient manner.

With these and other objects in view, aswill be apparent to thoseskilled in the art, the invention resides in the combination of partsset forth in the specification and covered by the claims appendedhereto.

Referring to the drawings illustrated one embodiment of the invention,and in which like reference numerals indicate like parts,

Fig. l. is a vertical longitudinal section through a steam generator,taken on the line il of Fig. 2;

Fig. 2 is a section taken on the line 2-2 of Fig. 1;

Fig. 3 is a section taken'on the line 33 of Fig. 1;

Fig. 4 is an enlarged fragmentary section taken on the line 4-4 of Fig.1;

Fig. 5 is an enlarged fragmentary elevation showing the constructionemployed for the front and rear walls of the ignitionchamber; and

Fig. 6 is a section taken on the line 6-6 of Fig. 5.

The embodiment illustrated comprises a fuel burning furnace Ill whichincludes an ignition chamber II, a combustion chamber l2 directlybeneath the ignition chamber, and an ash pit l4 directly beneath thecombustion chamber. The ignition chamber H is provided with a roof [5,side walls 16, a front wall I1, and a rear wall It. The front wall llslopes downwardly and forwardly, and the rear wall l8 slopes downwardlyand rearwardly, so that the ignition chamber flares downwardly. Thecombustion chamber i2 is provided with side walls 20, a front wall 2|,and a rear wall 22. The lower portion 23 of the front wall 2| slopesdownwardly and rearwardly to the ashpit M. A suitable fuel, such aspulverized anthracite, is transported in a current of primary airthrough pipes 25 to burners 26, which project the fuel downwardlythrough the roof I5 of the ignition chamber ll. These burners arearranged in two transverse rows in a staggered formation, and they areof the well-known "fishtail type with the larger dimension extending ina front to rear direction.

The hot gases escape rearwardly from the lower portion of the combustionchamber l2 through an outlet opening 2'! located beneath the lower edgeof the rear wall 22 and immediately above the ash pit [4. This opening21 has an appreciable height and it extends throughout substantially theentire width of the combustion chamber, so that a large area is providedfor the flow of gases at a comparatively low velocity. The opening 21leads directly into the lower portion of an upright passage 28 locatedimmediately to the rear of the furnace Ill and containing a superheater25 formed of vertically looped tubes each of which is connected at oneend to a discharge header 30 and at the other end to a transversesteam-and-water drum 3|. This drum is located behind the upper portionof the passages 28. A transverse water drum 33 is provided heneath thedrum 3|, and these drums are connected by a bank of upright water tubes34. A transverse balile 35 extends downwardly from the upper drum 3i,and the parts are so arranged that the gases will flow rearwardly fromthe upper end of the passage 28, then downwardly in contact with thewater tubes in front of the baffle 35, and then upwardly in contact withthe water tubes behind the baffle to a duct 37. From this duct 31 thegases travel downwardly through the tubes 38 of an air heater S9 andescape through a 3 duct 40 leading to a suitable induced draft fan orstack (not shown).

Water wall tubes are provided adjacent the various walls of the furnaceIll and of the passage 28. These tubes not only form efiicient steamgenerating devices, but they also protect the walls from excessive heatand they aid in supporting the walls. For this purpose a transverseheader 42 is provided adjacent the top of the rear wall of the ashpitl4, and a transverse header 43 is provided adjacent the top of the frontwall of the ashpit. A row of downcomer tubes 44 connect the lower waterdrum 33 with the header 42. Tubes 45 connect the two headers 42 and 43,so that both headers are supplied with water in ample quantities.

A row of water tubes 46 extend upwardly and rearwardly from the rearheader 42 along the bottom wall of the passage 28 and thence upwardlyalong the rear wall of the said passage to the upper drum 3!. Watertubes 41 extend upwardly and rearwardly from the rear header 42 acrossthe furnace outlet 21, along the rear side of the wall 22 and thenupwardly through the passage 28 to the drum 3!. Water tubes 48 extendupwardly and rearwardly from the rear header 42 across the furnaceoutlet 21 and along the front side of the wall 22, whereupon the tubesare divided so that some of them extend along the rear wall N3 of theignition chamber II and others extend along the front wall of thepassage 28, the upper ends of all these tubes being connected to thedrum 3!. The tubes 41 and 48 extend across the outlet 21 in the form ofan upwardly and rearwardly inclined bank containing several rows oftubes, the tubes in each row being widely spaced (see Fig. 4) to providea comparatively open screen through which the gases travel. A row ofwater tubes 50 extend upwardly from the front header 43, and along thesloping wall 23 and the upright front wall 2| of the combustion chamberto a transverse header located adjacent the junction of the walls 21 andI1. A row of water tubes 52 extend upwardly from this header 5| adjacentthe wall ll, thence rearwardly beneath the roof l5, and thence stillfurther rearwardly to connect with the drum 3|. Adjacent each side ofthe furnace there is provided a longitudinally extending lower header 54which is supplied with water from the end portions of the lower drum 33by means of feeder tubes 55. Water wall tubes 56 extend upwardly fromeach header 5A to an intermediate header 5'! near the top of the wall20, and from this intermediate header other water wall tubes 58 extendupwardly adjacent the wall I6 to an upper header 59. The upper headers59 are connected to the drum 3! by means of releaser tubes 60. As shownin Fig. 2, the water wall tubes 58 are preferably covered withrefractory material in order to avoid undue cooling of the ignitionchamber I l, but for clearness of illustration the end portions of thesetubes have been shown in full in Fig. 1. The portions of the tubes 48and 52 associated with the front and rear walls I! and [8 of theignition chamber are likewise covered with refractory material.

The air for combustion of the fuel is supplied in a new and highlyadvantageous manner. The burners 26 are enclosed in an air pressurechamber 62, the roof l5 forming the bottom wall of this chamber, andthis roof is provided with openings 63, generally rectangular in shape,through which the burner nozzles extend. These openings 63 are somewhatlarger than the nozzles air.

so that air may be blown downwardly around the fuel jets. This air maybe described as secondary air, and the air which carries the fuelthrough the pipes 25 to the burners may be described as primary air. Airmay be supplied under pressure from a suitable forced draft fan (notshown) to the inlet 65 of the air heater 39, and after travelingupwardly through the air heater this air will flow forwardly through twoducts 66 extending along opposite sides of the furnace. Branch ducts B!(Fig. 2), provided with dampers 68, connect the ducts 66 with the endsof the air chamber 62. The front and rear walls I! and I8 of theignition chamber H are provided with a multiplicity of openings 10through which air may enter to complete the combustion of the fuel, andthis air may be described as tertiary These air openings are distributedboth vertically and horizontally over a considerable area of each of thesloping walls I! and I8. Preferably these openings 10 are formed byspecial blocks H of refractory material which interlock with theadjacent water tubes, as shown particularly in Figs. 5 and 6. In orderto supply air to these openings 10, an air chamber 13 is provideddirectly in front of the wall l1, and an air chamber 14 is provideddirectly behind the wall I8, between the said wall and the gas passage28. The chamber 13 is connected to the air ducts 66 by branch ducts 15provided with dampers 16, and the chamber 14 is connected to the airducts 66 by branch ducts 1'! provided with dampers 18.

The operation of the invention will now be apparent from the abovedisclosure. Streams of pulverized fuel and primary air flow through thepipes 25 and are discharged downwardly from the burner nozzles 26 intothe ignition chamber II. Since the walls of this chamber are lined withrefractory material, a comparatively high temperature will be maintainedand ignition will take place promptly. Ignition will also be facilitatedby the fact that a relatively small portion of the total air requiredfor combustion enters with the fuel. Air from the preheater 39 flowsforwardly through the ducts B6 and thence through the branch ducts 3'!(under the control of the dampers 68) into the chamber 62, whence it isdischarged downwardly as secondary air through the openings 63 aroundthe burners. Air also flows from the ducts 66 through the branch ductsl5 and I! (under control of the dampers l6 and 18) to the chambers 13and M respectively. From these chambers this air enters the ignitionchamber as tertiary air through the openings 1!! in the front and rearwalls of the ignition chamber, and mixes with the fuel to complete itscombustion during the flow down wardly through the combustion chamber I2. This mixing is facilitated by reason of the staggered burnerarrangement, since this allows air to flow into direct contact with boththe front and the rear portions of each fuel jet, in addition to thelateral portions thereof. Most of the ash is deposited directly in theash pit M. The hot gases travel rearwardly at a relatively low velocitypast the lower portions of the Water tubes 48 and 47 and through theopening 21 into the passage 28. Some of the ash will be carried out ofthe combustion chamber by the gases, and a large part of this so-calledfly ash will be deposited on the inclined floor of the passage 28 andslide forwardly along this floor into the ash pit. As the gases travelupwardly through the passage 28 they will make contact with thesuperheater 29. The gases will then make one downward pass and oneupward pass in contact with the water tube bank 34, after which theywill travel downwardly through the air heater tubes 38 and escapethrough the outlet 49. Steam will be generated in the water tubes 46,41, 48, 50, 52, 58 and 58, and this steam will be delivered to the drum3i and thence to the superheater 29. An ample supply of water will bedelivered from the drum 33 to the lower ends of the steam generatingtubes through the down-comer tubes 44, 45 and 55.

Since air is supplied through both the front wall I! and the rear walll8, both the front portion and the rear portion of the flame envelopeare in contact with air. This is of the greatest importance, since itmakes possible the completion of combustion during the downward travelof the fuel and before the gases pass through the opening 21 into thepassage 28. Consequently the losses resulting from unburned carbon willbe very low. Furthermore, there will be no danger of injuring thesuperheater 29 by reason of delayed combustion in the passage 28. Theignition chamber II, with its refractory lined walls, acts as aheat-reflecting retort which maintains a very high temperature andgreatly facilitates prompt ignition of the fuel. The invention isaccordingly well adapted for burning low volatile fuels, such asanthracite.

Having thus described my invention, what I claim as new and desire tosecure by Letters Patent is:

1;- Fuel burning apparatus comprising walls forming an ignition chamberand including a front wall and a rear wall, and means to project fueldownwardly into the ignition chamber for combustion in suspension, thefront wall sloping downwardly and forwardly and the rear wall slopingdownwardly and rearwardly, the said front and rear walls including watertubes and '1, in which the specified water tubes extend upwardly alongthe sloping front'and rear walls, I

blocks of refractory material mounted on the water tubes to shield themfrom the heat ofthe combustion, and the said blocks being shaped toprovide openings for the admission of air to the fuel from opposingdirections.

ing along the top of the ignition chamber, the

burners in one row being staggered relative to the burners in the otherrow, so that the air admitted through the specified air openings mayhave direct access to each fuel jet from both the front and the rear. I

3. Fuel burning apparatus as set forth in claim and the tubes in each ofsaid walls are spaced apart with the refractory blocks located betweenthem. 4. Fuel burning apparatus as set forth in claim 1, in which thespecified air openings are distributed both vertically and horizontallyover a considerable area of each of the front and rear walls. 1

MAX H. KUHNER.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS

